It is a striking fact that the letters which we take for granted today, in printed books, derive for the most part from handwriting in the last centuries of the Roman empire. Indeed the script in fragments of Latin messages, written by members of the Roman garrison at Hadrian's Wall in about100, is visibly related to the letters taught in western European languages in the 20th century.

When Christian monks in western Europe write out their holy texts, they do so in Latin on parchment - in the relatively new form of the codex. The script they use is that of the Roman empire, but there are many regional variations.

Manuscripts written in Italy in the 7th to 8th centuryare entirely in capital letters, giving a neat and intensely formal look. But Celtic monks in Ireland, who are among the most prolific of scribes at this time, prefer a more workaday script (the everyday hand of the Roman legionaries at Hadrian's Wall must have survived in many outlying regions as the normal style of handwriting).

A very early surviving example is the so-called Cathach of St Columba (cathach meaning 'battler', because this book of psalms is believed to have been carried into battle as a sacred talisman).

The Cathach of St Columba, dating perhaps from the early 7th century and possibly written by the saint himself, also exemplifies one profoundly influential innovation of the Irish monks. To emphasize the beginning of an important passage, the scribes write its first letter much larger than the rest of the text and in a grander style. Slightly embarrassed by the difference in scale, they tend to reduce each succeeding letter by a little until reaching the small scale of the ordinary text.

Here, already, is the distinction between capitals and lower case (or in manuscript terms, majuscule and minuscule) which is later a standard feature of the western European script.

The early Christian manuscripts influence the later standards of calligraphy and of print in two widely separated stages.

At the court of Charlemagne, in the 8th century, the existing manuscript traditions are deliberately tidied up into one official style of exquisite clarity. This becomes cluttered again during the later Middle Ages, until calligraphers of the Renaissance, in the 15th century, rediscover the earlier style. From them, still within the spirit of the Renaissance, it is adopted by the early printers - and thus enshrined for succeeding centuries.

The Carolingian script: 8th century

In780 the emperor Charlemagne meets Alcuin, a distinguished scholar from York, and invites him to direct his palace school at Aachen. Twelve months or more later, in October 781, Charlemagne commissions from a scribe, by the name of Godesalc, a manuscript of the gospels. Godesalc completes his magnificent book for the emperor in April 783. The Godesalc Evangelistary, as it is now called, is the first book in which the script known as Carolingian minuscule appears. The text uses conventional capitals, but the dedication is in these lower-case letters.

It is probably not too fanciful to see the influence of Alcuin, recently arrived at court, in Godesalc's experiment with this new script.

Over the next two decades Alcuin rigorously researches and refines a new calligraphy for Charlemagne's new empire. Just as Charlemagne sees himself as a Roman emperor, so Alcuin goes back to Rome for his inspiration. With a passion and a thoroughness which prefigures the scholars of the Renaissance, he copies the letters carved on Roman monuments or written in surviving manuscripts and selects from them to establish a pure classical style - with the addition of the minuscule letters of monastic tradition.

The results are superb. Carolingian manuscripts (produced in large numbers in a monastery at Tours, of which Alcuin becomes abbot in 796) are among the most clear and legible documents in the history of writing.

Black-letter style: 11th - 15th century

In the later Middle Ages, the clarity of the Carolingian script becomes lost. A much darker and denser style evolves in northern Europe from the 11th century. It is known as 'black letter', because of the almost oppressive weight of dark ink on each densely packed page.

This medieval style derives partly from an aesthetic impulse (there is drama in dark pen strokes and in the angular ends left by a broad nib), but it is above all a matter of economy. Parchment is expensive. Books are much in demand, particularly with the growth of universities. If the letters in a word and the words in a sentence are squashed more closely together, less pages are used and the book is cheaper.

The black-letter style is the convention in German manuscripts when printing is developed there in the 1450s. It therefore becomes the type face used for the earliest European printed books, such as Gutenberg's Bible. Angular letters of this kind remain the normal convention in German books until the early 20th century.

But within the first century of printing there is a reaction in Italy against this heavy style. Italian humanists of the Renaissance associate it with all that they consider dark and barbarous about the Middle Ages. Like medieval architecture, it is given the dismissive name of Gothic.

Roman and italic: 15th century

Italian scholars of the 14th and 15th century, followers of Petrarch in their reverence for classical culture, search through libraries for ancient texts. Copying out their discoveries, they aspire also to an authentic script. They find their models in beautifully written manuscripts which they take to be Roman but which are in fact Carolingian.

The error is a fortunate one. The script devised for Charlemagne's monastic workshops in the 8th century is a model of clarity and elegance. It is adapted for practical use, in slightly different ways, by two Florentine friends - Poggio Bracciolini and Niccolò Niccoli.

Bracciolini, employed as secretary at the papal court in Rome from 1403, uses the ancient script for important documents. To the rounded lower-case letters of the the Carolingian script he adds straight-edged capital letters which he copies from Roman monuments.

By contrast his friend Niccoli adapts the Carolingian script to the faster requirements of everyday writing. To this end he finds it more convenient to slope the letters a little (the result of holding the pen at a more comfortable angle), and to allow some of them to join up. Joining up is not in itself new. In several forms of medieval hand-writing the letters flow together to become what is known as a 'cursive' hand.

Printers in Venice later in the century, attempting to reflect the classical spirit of humanism, turn to the scripts of Bracciolini and Niccoli. The rounded but upright style of Bracciolini is first used by the French printer Nicolas Jenson shortly after his arrival in the city in 1470. This type face is given the name roman, reflecting its ancient origins.

In 1501 another great Venetian printer, Aldus Manutius, needs a contrasting and smaller type for a 'pocket edition' of Virgil. He turns to the script of Niccoli, in everyday use by fashionable Italians, and calls it accordingly italic. Roman and italic eventually become a standard part of every printer's repertoire.

Copperplate: from the 16th century

For purposes of handwriting a version of the italic script eventually becomes the norm in most western societies. The reason is partly accidental. Flowing letters are easily engraved, as can be seen in the captions of any engraving. The natural movement of the burin through the metal is in elegant curves, ending in elongated points. A nib, filled with ink, can easily make the same flowing marks on paper.

As writing becomes a necessary accomplishment for the middle classes, a new profession is created - that of the writing master.

The writing master needs examples for his pupils to copy. The engraver provides these, as separate sheets or as plates bound into manuals, and the manuals soon have the effect of standardizing handwriting. The conventional form becomes known as copper-plate - imitating the letters which the engraver has cut in his copper plate.

Many such manuals are published, starting with the Essemplare ('Examples') of Gianfrancesco Cresci, a Vatican writer, in 1560. The most successful collection of copper-plate examples is the Universal Penman of George Bickham, first published in 1733 and still in use as a teaching aid in Britain in the early part of the 20th century.